Can't launch firefox

well i just tried to update to firefox 1.5.0.2 with disatrous results it seems. the install wouldn't work, so i removed it and re installed mozilla-firefox, but now that won't work if i try to launch firefox i get:
Xlib: connection to ":0.0" refused by server
Xlib: XDM authorization key matches an existing client!

and if i try to launch mozilla-firefox:
Xlib: connection to ":0.0" refused by server
Xlib: XDM authorization key matches an existing client!

ok now when i run mozilla-firefox from terminal i get this:
Extension System Warning: Failed to set up default extensions files probably because you do not have write privileges to this location. While you can run Firefox like this, it is recommended that you run it at least once with privileges that allow it to generate these initial files to improve start performance. Running from a disk image on MacOS X is not recommended.

But the screen is blank, and i can't seem to run it as root or sudo; when i try i get:

I'm running Debian sarge, i tried to install firefox 1.5 using backports:
apt-get -t Sarge-backports install firefox
immediately after this, firefox stopped working. I realize i didn't remove the mozilla firefox first, so i tried that:
apt-get remove mozilla-firefox
but firefox1.5 still wouldn't work, so i tried manually removing the 1.5 install by deleting:
/usr/lib/firefox
following a post i read online somewhere (lost the page)
I've reinstalled mozilla-firefox:
apt-get install mozilla-firefox
which was not working at first, but now gives the extension system warning i posted last time and is EXTREMELY slow.

Well i managed to get firefox 1.0 working again, so i this time i downloaded the firefox1.5 files from http://www.backports.org and i installed them, but it still won't work. i get these messages when i run from terminal :
wraithfire@Hellfury:~$ firefox
Segmentation fault
and :
Hellfury:/home/wraithfire# firefox
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

(firefox-bin:3860): Gtk-WARNING **: cannot open display:
no i decided to ldd firefox-bin again, and so i [CODE} locate firefox-bin [/CODE] and it pointed me to the wrong directory, /usr/lib/mozilla-firefox/firefox-bin. after some searching i found that the correct path was /usr/lib/firefox/firefox-bin and i ldd it

seems like it detects the file, but it still doesn't work. when i run this:

Code:

/usr/lib/firefox/firefox-bin

the cursor just hangs with blank return and ^c doesn't return the prompt. all other attempts to start it return the same errors as before, segmentation fault as normal user or
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

(firefox-bin:3856): Gtk-WARNING **: cannot open display:
as root or sudo